Wording for a letter to vacant home owner, financing

Hello!

Anyone have suggestions to word a letter to an owner of the house I am interested in buying to rehab? Also, does anyone have any suggestions on creative, attractive formulation of the contract where we don’t have to shell out the full purchase price for the rehab right away, but pay in, say 60-90 days after giving a deposit? Any suggestions will be greatly appreciated!

Olga